Java is a high-level, object-oriented programming language used to build web apps, mobile applications, and enterprise software systems.
- Java is a platform-independent language, which means code written in Java can run on any device that supports the Java Virtual Machine (JVM).
- Syntax and structure are similar to C-based languages like C++ and C#.
Basic Code Example
The following is a simple program that displays the message “Hello, World!” on the screen.
public class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello World!");
}
}
Output
Hello World!
Why Learn Java?
- Used to build Android apps, desktop and web apps, enterprise backend systems, and cloud-based software.
- In high demand with many job opportunities in software development.
- Has popular frameworks like Spring and Hibernate which makes it powerful for enterprise applications.
- Supports object-oriented programming for clean, maintainable and reusable code.
- Top companies like Amazon, Netflix, and LinkedIn use Java.
Getting Started with Java
Getting started with Java, its basic concepts form the foundation of your programming journey, covering essential topics such as syntax, data types, variables, loops, and conditional statements.
- Introduction
- Download and Install Java
- JDK vs JRE vs JVM
- Identifiers
- Keywords
- Data Types
- Wrapper Classes
- Variables
- Operators
- Decision Making
- Loops and Jump Statements
- Project: Number Guessing Game
Methods
Java methods are reusable blocks of code that perform specific tasks and help organize your program. They improve code readability, reduce repetition, and make debugging easier.
- Introduction
- Static Methods vs Instance Methods
- Access Modifiers
- Command Line Arguments
- Variable Arguments (Varargs)
Arrays
Java arrays are containers that store multiple values of the same data type in a single variable. They provide an efficient way to manage and access collections of data using index-based positions.
- Introduction
- Multi-Dimensional Arrays
- Jagged Arrays
- Arrays Class
- Final Arrays
- Projects: Tic-Tac-Toe Game
Strings
Java Strings represent sequences of characters and are widely used in text processing. They are immutable, meaning once created, their values cannot be changed.
- Introduction
- Why Strings are Immutable
- String Concatenation
- String Methods
- String Class
- StringBuffer Class
- StringBuilder Class
- Strings vs StringBuffer vs StringBuilder
OOP Concepts
Java follows the Object-Oriented Programming (OOP) paradigm, which organizes code into classes and objects. Core OOP principles like inheritance, encapsulation, polymorphism, and abstraction make Java modular and scalable.
- Introduction
- Classes and Objects
- Constructors
- Object Class
- Abstraction
- Encapsulation
- Inheritance
- Polymorphism
- Packages
- Project: Simple Banking Application
Interfaces
Java interfaces define a contract that classes must follow, specifying method signatures without implementations. They enable abstraction and support multiple inheritance in Java through a clean, structured approach.
- Interfaces
- Class vs Interface
- Functional Interface
- Nested Interface
- Marker Interface
- Project: Employee Management System
Exception Handling
Java Exception Handling is a mechanism to handle runtime errors, ensuring the program runs smoothly without crashing. It uses keywords like try, catch, throw, throws, and finally to manage exceptions.
- Introduction
- Try-Catch Block
- Final, Finally and Finalize
- Throw and Throws
- Customized Exception Handling
- Chained Exceptions
- Null Pointer Exceptions
- Exception Handling with Method Overriding
Regex
Java Regex (Regular Expressions) allows pattern matching and text manipulation using the java.util.regex package. It is powerful for validating, searching, and replacing strings based on specific patterns.
Memory Allocation
Java Memory Allocation refers to how memory is assigned to variables, objects, and classes during program execution. It involves stack and heap memory, with the JVM managing allocation and garbage collection automatically.
- Java Memory Management
- How Java Objects Stored in Memory?
- Types of Memory Areas Allocated by JVM
- Stack vs Heap Memory Allocation
- Garbage Collection
- Types of JVM Garbage Collectors
- Memory Leaks
Collections
Java Collections provide a framework for storing and manipulating groups of objects efficiently. It includes interfaces like List, Set, and Map, along with classes like ArrayList, HashSet, and HashMap.
- Collections Class
- Collection Interface
- List Interface
- ArrayList
- LinkedList
- Set Interface
- HashSet
- Linked HashSet
- TreeSet
- Queue Interface
- Priority Queue
- Deque Interface
- Map Interface
- HashMap
- Iterator
- Comparator Interface
- Comparable Interface
- Project: Face Detection System
Lambda Expressions and Streams
Java Streams and Lambda Expressions simplify data processing by enabling functional-style operations on collections. Lambdas provide concise syntax for anonymous functions, while Streams allow efficient filtering, mapping, and reduction of data.
Multithreading and Synchronization
Java Multithreading allows concurrent execution of two or more threads, enabling efficient CPU utilization and faster program performance. It is commonly used for tasks that required parallel processing and responsiveness from multiple ends.
- Introduction
- Threads
- Thread.start() vs Thread.run() Method
- Thread.sleep() Method
- Runnable Interface
- Main Thread
- Thread Priority in Multithreading
- Daemon Thread
- Java Synchronization
- Thread Safety
- Locks in Java
- Lock vs Monitor in Concurrency
- Lock Framework vs Thread Synchronization
- Reentrant Lock
- Deadlock in Multithreading
- Thread Pools
- Executor Framework
- Project: Snake Game
File Handling
Java File Handling enables programs to create, read, write, and manipulate files stored on the system. It uses classes from the java.io and java.nio packages for efficient file operations.
- Introduction to Java IO
- Reader Class
- Writer Class
- File Handling
- File Class
- FileInputStream
- FileOutputStream
- FileReader Class
- FileWriter Class
- FileOutput Stream
- BufferedReader Input Stream
- BufferedReader Output stream
- FilePermission Class
- FileDescriptor Class
- Project: Text Editor
Networking
Java Networking enables communication between devices over a network using classes from the java.net package. It supports protocols like TCP and UDP for building client-server applications and data exchange.
Java Database Connectivity(JDBC)
Java Database Connectivity (JDBC) enables Java applications to connect and interact with databases for storing and retrieving data efficiently.
Java Chapter-wise Practice Quiz
Java chapter Wise Quiz helps learners test their understanding of individual Java concepts through short, focused quizzes on each topic, making revision and practice more effective.
Java Basics, Variables, Operator, Control Statements and Loops, Methods, Arrays, Array Class, String Basics, String Classes, Classes and Objects, Constructors, Inheritance and Abstraction, Polymorphism and Packages, Interfaces, Interface types and Comparator, Java Exceptions, Exception Handling, Regex Basics and Pattern Matching, Java Memory Allocation, Heap vs Stack, JVM Memory Management and Garbage Collection, Collection, List, ArrayList, LinkedList, Set and HashSet, Queue and Map Interface, Iterators, Comparator vs Comparable, Lambda Expressions and Streams, Thread Basics and Lifecycle, Thread Methods and Daemon Threads, Synchronization Basics, Deadlocks and Synchronization, File Handling, File Writing, Networking Basics and Protocols, Sockets and Server Communication, JDBC.
Interview Questions
This section provides a collection of commonly asked Java interview questions and answers to help you prepare for technical interviews.